1. Field of the Invention
The present invention relates to a film coating nozzle for applying coating material to a surface of a product such as a compressor piston, used in an arrangement which requires wear resistance and liquidtightness, and thereby forming film on the surface of the product, and an apparatus and a method for coating a compressor piston using the same. More particularly, the present invention relates to a film coating nozzle which can spread, by a dispenser method, applied coating material to form film of a uniform film thickness, and an apparatus and a method for coating a compressor piston using the same, which can coat the compressor piston through a series of continuous processes.
2. Description of the Related Art
Generally, a product such as a compressor piston used in an arrangement requiring wear resistance and liquidtightness is coated on its surface with film of a predetermined thickness. This coating technique has already been employed in various industrial fields. As well known in the art, in this coating technique, it is important that the thickness be uniform over the entire surface of the applied film. Specifically, while, for example, a Teflon coating is applied to a circumferential outer surface of a head part of the compressor piston, upon coating the compressor piston, a thickness and uniformity of a coated film greatly influence the performance of a compressor, and therefore should be carefully controlled.
As coating methods for improving wear resistance and liquidtightness of a compressor piston, powder coating, spraying or electrostatic painting are well known in the art. However, these coating methods suffer from disadvantages in that variance in thickness of coated film is substantial. In particular, in a spray coating method, since a coating process is involved and sprayed coating material spatters, regions which do not require application of coating material are also coated with coating material and thus, coating material is excessively wasted. Further, in the spray coating method, a surrounding environment is polluted by coating material which spatters during a coating procedure.
To cope with these problems occurring in the conventional spray coating method, coating apparatuses are disclosed in Japanese Patent Laid-open Publication No. Heisei 8-173893 and International Patent Application No. PCT/JP00/00096. Each of the coating apparatuses has a rotation support device which rotatably supports a cylindrical product to be coated, a coating material injecting device which is installed above the rotation support device in such a way as to be moved upward and downward and has a nozzle for applying coating material to a circumferential outer surface of the product rotated by the rotation support device, and a blade which spreads to a uniform film thickness coating material applied to the circumferential outer surface of the product by the coating material injecting device in such a way as to remove excess coating material.
However, the conventional coating apparatuses still encounter problems in that, since the blade for removing excess coating material applied to the circumferential outer surface of the cylindrical product must be installed separately from the nozzle at a position adjoining the rotating cylindrical product, a construction of each coating apparatus as a whole is complex. Moreover, because driving and controlling of the blade serving as a coating material spreading device is complicated, maintenance and repair costs and time of the coating apparatus are increased.
Furthermore, in the conventional coating apparatuses, while it is possible to apply coating material, for example, to a circumferential outer surface of a head part of a compressor piston, it is impossible to apply coating material to a bridge part of a piston for a fixed displacement swash plate type compressor or wing parts of a piston for a variable displacement swash plate type compressor. For this reason, in the conventional art, a coating process for the bridge part or wing parts should be performed by a spraying method, in a state wherein the piston which is coated with coating material on its circumferential outer surface is moved to another place or apparatus. Hence, by the fact that two different methods are employed, operation control for the entire coating apparatus is made further complicated. Also, inherent problems of the spray coating method, which are related with increase in coating material consumption and pollution of surrounding devices due to spatter of coating material, still exist.
One aspect of the present invention provides a coating apparatus. The apparatus comprises a nozzle comprising at least one inlet and at least one outlet, each inlet being configured to receive a coating material from a source thereof, each outlet being configured to flow out the coating material on a surface for coating; and a spreader integrated with the nozzle and configured to spread the coating material over the coating surface. The apparatus further comprises a spacer integrated with the nozzle and configured to maintain a distance from the nozzle and spreader to the coating surface substantially constant. The spacer comprises an elongated projection from the nozzle, and wherein the elongated projection comprises a tip configured to contact the coating surface. The spacer and the nozzle are configured to move relative to the coating surface in a direction while coating, and wherein the spacer is so located as to lead each outlet of the nozzle in the direction of the relative movement. The at least one outlet comprises a longitudinal opening. The at least one outlet comprises a substantially circular or elliptical opening. The at least one outlet comprises three or more circular or elliptical openings. Each of the three or more openings has a different size from each other. The three or more openings are linearly arranged. Each of the three or more openings has a different size from each other, and wherein the three or more openings are linearly arranged such that the size of the openings are increasing in a direction of the linear arrangement. The nozzle comprises a distal portion, and wherein each outlet is located in the distal portion.
A part of the distal portion constitutes the spreader. The nozzle comprises a distal surface, on which each outlet is opened. At least a partial area of the distal surface is configured to contact the coating material. The nozzle is configured to move relative to the coating surface in a direction while coating, and wherein the distal surface is slanted with reference to the direction of the relative movement. The nozzle is configured to flow the coating material in a direction at each outlet, and wherein the distal surface is slanted with reference to the direction of the flow. The spreader comprises at least a part of the distal surface configured to contact the coating material. The nozzle and spreader are configured to move relative to the coating surface in a direction while coating, and wherein the spreader comprises an trailing edge of the distal surface in the relative movement. he spreader comprises an edge of the distal surface. The spreader is configured to flow the coating material along the at least a partial area of the distal surface while coating so as for the spreader and the coating surface to sandwich the coating material with a predetermined thickness along the edge. The nozzle is configured to move relative to the coating surface in a direction while coating, wherein the distal surface comprises a leading edge and a trailing edge in the relative movement of the nozzle, and wherein the distal surface is slanted such that the trailing edge is closer to the coating surface than the leading edge is.
The spreader comprises a spreading surface and an edge of the spreading surface. The spreading surface and the edge are configured to contact the coating material. The spreader is configured to flow the coating material along the spreading surface so as for the spreading surface and the coating surface to sandwich the coating material with a predetermined thickness along the edge. The spreading surface is plain and/or curved. The spreader further comprises a protrusion from the spreading surface or a groove into the spreading surface. The protrusion is configured to correspond to a recess on the coating surface, and wherein the groove is configured to correspond to a projection from the coating surface. The spreading surface is located in proximity to each outlet. The spreader is configured to move relative to the coating surface in a direction while coating, and wherein the surface is slanted with reference to the direction of the relative movement. The surface has a tangent, and wherein the surface is slanted such that the tangent of the surface and the direction of the spreader""s relative movement have an acute angle therebetween.
The nozzle and spreader are configured to move relative to the coating surface while coating. The spreader is configured to spread the coating material over the coating surface in a substantially uniform thickness. The apparatus further comprises a mechanism configured to move the nozzle vertically and horizontally. The apparatus further comprises a controller configured to control overall operation of the apparatus. The apparatus further comprises a support configured to support an object comprising the coating surface. The support is capable of rotating the object about an axis. The apparatus further comprises one or more other nozzles, each of which is configured to flow one or more coating materials. The apparatus further comprises a spreader integrated with each of the one or more other nozzles. The apparatus further comprises another spreader not integrated with the nozzle and configured to further spread the coating material over the coating surface in a substantially uniform thickness.
Another aspect of the present invention provides a film coating apparatus. The apparatus comprises means for flowing a coating material on a surface for coating; and means for spreading the coating material over the coating surface, wherein the flowing means and spreading means are integrated in a single body. The apparatus further comprises means for moving the single body of the flowing means and spreading means relative to the coating surface. The spreading means is configured to spread the coating material over the surface in a substantially uniform thickness. The spreading means comprises a spreading surface configured to contact the coating material and a spacer configured to maintain a distance between the spreading surface and the coating surface substantially constant.
Another aspect of the present invention provides a method of making a coating apparatus. The method comprises: providing a nozzle comprising a distal portion and at least one outlet in the distal portion, wherein each outlet is configured to flow a coating material on a surface for coating; and providing a spreader comprising a spreading surface and an edge thereof in the distal portion of the nozzle, wherein the spreader is configured to flow the coating material along the spreading surface so as for the spreader and the coating surface to sandwich the coating material, and wherein the spreader is further configured to keep the sandwiched coating material in a substantially constant thickness along the edge while coating. The provision of the nozzle and the spreader comprises molding with a mold comprising structures corresponding to the nozzle and the spreader. The provision of the nozzle and the spreader providing further comprises post-mold treatments. The method further comprises: obtaining topological information of the coating surface of an object; and designing the spreading surface and the edge based on topological information. The spreading surface is plain and/or curved. The spreader further comprises a protrusion from the spreading surface and/or a groove into the spreading surface. The protrusion is configured to correspond to a recess on the coating surface, and wherein the groove is configured to correspond to a projection from the coating surface. The method further comprises providing a spacer integrated with the nozzle.
A further aspect of the present invention provides a method of coating an object. The method comprises: providing an object comprising a surface for coating; providing a coating apparatus comprising a nozzle and a spreader, the nozzle and spreader being integrated in a single body; providing a coating material on the coating surface with the nozzle; and spreading the coating material over the coating surface with the spreader. The method he provision of the object comprises supporting the object with a support capable of rotating the object about an axis. The method further comprises moving the single body relative to the coating surface of the object. The moving comprises at least one of a movement of the single body and a movement of the object. The movement of the single body comprises moving at least one of vertical and horizontal directions. The movement of the object comprises rotating the object about an axis. The nozzle comprises at least one inlet and at least one outlet, and wherein the provision of the coating material comprises receiving the coating material from a source thereof through each inlet, and flowing out the coating material on the coating surface through each outlet. The act of spreading substantially homogenizes a thickness of the coating material over the coating surface. The act of spreading comprises forcing the coating material on the coating surface with the spreader in a direction. The spreader comprises a spreading surface and an edge thereof, and wherein the act of spreading comprises sandwiching the coating material between the spreading surface and coating surface. The act of spreading further comprises maintaining the sandwiched coating material in a substantially constant thickness along the edge. The act of maintaining comprises contacting the coating surface with a tip of an elongated spacer attached to coating apparatus. The provision of the coating apparatus comprises providing more than one nozzle and spreader. Each of the more than one nozzle is integrated with one of the more than one spreader. The provision of the coating material comprises providing one or more coating materials on more than one coating surface of the object with the more than one nozzle. The act of spreading comprises spreading the coating material on the more than one coating surfaces with the more than one spreader. The act of spreading further comprises further-spreading the coating material over the surface in a substantially uniform thickness with another spreader not integrated with the nozzle. The method further comprises determining a local topography of the surface for coating; and providing the coating apparatus, the spreader of which has a spreading configuration matching with the topography. The object comprises a piston or an intermediate product therefor. The piston is one for use with a swash plate type compressor.
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to allow coating material to be spread at the same time with application, by coating material spreading means integrally formed with a nozzle, to thereby form film of a uniform thickness, whereby the need for a separate blade for removing excess coating material is obviated.
Another object of the present invention is to provide coating material spreading means formed integrally with a nozzle, to thereby simplify an entire construction of a coating apparatus.
Still another object of the present invention is to provide a coating apparatus and method which allow a head part, a bridge part or wing parts as a frictional part of a compressor piston to be coated through a series of continuous processes.
According to one aspect of the present invention, there is provided a film coating nozzle comprising: a nozzle body configured to supply coating material; and at least one coating material spreading means defined with at least one coating material injection hole which is communicated with the inside of the nozzle body, and formed integrally with the nozzle body to spread to a uniform film thickness coating material applied through the coating material injection hole to a surface of a product, in such a way as to remove excess coating material. Here, the film coating nozzle according to this aspect of the present invention will be referred to as a xe2x80x9cfirst nozzlexe2x80x9d.
The first nozzle can be appropriately used to coat a circumferential outer surface of a cylindrical product to be coated, for example, a circumferential outer surface of a piston for a wobble plate type compressor. Due to the provision of the first nozzle, without installing the nozzle and a blade separately from each other, since it is possible to apply coating material by the coating material spreading means formed integrally with the nozzle body, and at the same time spread to a uniform film thickness applied coating material and thereby remove excess coating material, the need for the separate blade and means for driving and controlling the separate blade is obviated. Thus, constructional simplification of an entire coating apparatus can be accomplished, and the number of checkpoints for maintenance and repair of the coating apparatus can be decreased.
In the first nozzle, it is preferred that the coating material spreading means has a width which is equal to or slightly greater than that of a portion of the product, which is to be coated. Also, the at least one coating material injection hole defined in the coating material spreading means may comprise a single slot, a plurality of independent holes, or a combination thereof. The number and contour of the coating material injection holes can be changed depending upon a configuration of a product to be coated.
Further, in the case that the product to be coated comprises a compressor piston, an annular groove is defined on a circumferential outer surface of a head part of the piston. In this connection, it is preferred that a projection is formed at a position on a lower end surface of the coating material spreading means, which position corresponds to the annular groove, so as to control an amount of coating material applied in the annular groove.
Moreover, the lower end surface of the coating material spreading means is formed as an inclined surface having a predetermined inclination angle to ensure easy spreading of coating material. While it is preferred that, when a surface of the coating material spreading means which is positioned upstream in a rotating direction of the product is assumed to be a front surface, the inclined surface is inclined downward from the front surface toward a rear surface, it can also be envisaged that the inclined surface is inclined downward from the rear surface toward the front surface. Also, while it is preferred that the inclination angle of the inclined surface is within the range of an acute angle, it is to be readily understood that the present invention is not limited to such a provision.
According to another aspect of the present invention, there is provided a film coating nozzle adapted for coating a product, for example, a bridge part of a piston for a fixed displacement swash plate type compressor, comprising: a nozzle body configured to supply coating material; and a pair of coating material spreading means each defined with at least one coating material injection hole which is communicated with the inside of the nozzle body, and formed integrally at both sides of the nozzle body to spread to a uniform film thickness coating material applied through coating material injection holes to surfaces of the bridge part in such a way as to remove excess coating material, each coating material spreading means having a lower end surface which conforms to a surface contour of the bridge part. Here, the film coating nozzle according to this aspect of the present invention will be referred to as a xe2x80x9csecond nozzlexe2x80x9d.
In the second nozzle, it is preferred that each coating material spreading means has a width which is equal to or slightly greater than that of a portion of the bridge part of the piston, which is to be coated. Also in the second nozzle, the at least one coating material injection hole defined in each coating material spreading means may comprise a single slot, a plurality of independent holes, or a combination thereof. The number and contour of the coating material injection holes can be changed depending upon a configuration of a product to be coated. Further, while the second nozzle coats the product to be coated while being slid on the bridge part of the piston for the fixed displacement swash plate type compressor, the bridge part serving as the product to be coated, in order to ensure easy spreading of coating material, the lower end surface of each coating material spreading means can be formed as an inclined surface which is inclined in a direction opposite to movement of the second nozzle by a predetermined inclination angle. While it is preferred that the inclination angle of the inclined surface is within the range of an acute angle, it is to be readily understood that the present invention is not limited to such a provision. Further, in the second nozzle, it is preferred that a guide post is formed integrally with the nozzle body so that it is brought into sliding contact with the product to be coated, to prevent the second nozzle from fluctuating during movement thereof and allow film of a uniform thickness to be formed.
According to another aspect of the present invention, there is provided a film coating nozzle adapted for coating a product, for example, both wing parts of a piston for a variable displacement swash plate type compressor. Here, the film coating nozzle according to this aspect of the present invention can be constructed in the same manner as the second nozzle, and will be referred to as xe2x80x9canother second nozzlexe2x80x9d and has the same construction as the second nozzle, except that each coating material spreading means thereof has a lower end surface which conforms to a surface contour of each wing part of the piston for the variable displacement swash plate type compressor.
According to another aspect of the present invention, there is provided a compressor piston coating apparatus adapted for coating a piston for a fixed displacement swash plate type compressor using one of the above-mentioned nozzles, the apparatus comprising: rotation support means for rotatably supporting both ends of the piston; a pair of first coating material applying means installed above the rotation support means in a manner such that they can be moved upward and downward, the pair of first coating material applying means having a pair of first nozzles, respectively, which apply coating material to circumferential outer surfaces of both head parts of the piston rotated by the rotation support means, and at the same time spread to a uniform film thickness applied coating material and compressor piston coating apparatus adapted for coating a piston for a variable displacement swash plate type compressor using another one of the above-mentioned nozzles, the apparatus comprising: rotation support means for rotatably supporting both ends of the piston; first coating material applying means installed above the rotation support means in a manner such that it can be moved upward and downward, the first coating material applying means having a first nozzle which applies coating material to a circumferential outer surface of a head part of the piston rotated by the rotation support means, and at the same time spreads to a uniform film thickness applied coating material and thereby removes excess coating material, in a state where the first nozzle is placed adjacent to the circumferential outer surface of the head part of the piston; fixing means installed in the vicinity of the rotation support means fixedly support both ends of the piston; and second coating material applying means installed above the fixing means in a manner such that it can be moved upward and d and slid laterally, the second coating material applying means having another second nozzle which applies coating material to both wing parts of the piston fixedly supported by the fixing means, and at the same time is slid to spread to a uniform film thickness applied coating material and thereby remove excess coating material, in a state where the second nozzle is placed adjacent to the wing parts of the piston.
According to another aspect of the present invention, there is provided a method for coating the piston for the fixed displacement swash plate type compressor, by the compressor piston coating apparatus to which one of the above-mentioned nozzles is applied, the method comprising the steps of: rotatably supporting both ends of the piston by the rotation support means; lowering the pair of first coating material applying means so that coating material spreading means of their respective first nozzles are placed adjacent to both head parts of the piston; injecting coating material to the head parts of the piston through the first nozzles of the pair of first coating material applying means while rotating the piston, and spreading to a uniform film thickness coating material applied to the head parts of the piston and thereby removing excess coating material by coating material spreading means; raising the pair of first coating material applying means; conveying the piston with the coated head parts from the rotation support means to the fixing means by conveying means and fixedly supporting both ends of the piston by the fixing means; lowering the second coating material applying means so that respective coating material spreading means of the second nozzle are placed adjacent to the bridge part of the piston supported by the fixing means; and injecting coating material to the bridge part of the piston through the second nozzle while sliding the second coating material applying means in an axial direction of the piston, and spreading to a uniform film thickness coating material applied to the bridge part of the piston and thereby removing excess coating material by respective coating material spreading means of the second nozzle.
According to another aspect of the present invention, there is provided a compressor piston coating apparatus adapted for coating a piston for a variable displacement swash plate type compressor using another one of the above-mentioned nozzles, the apparatus comprising: rotation support means for rotatably supporting both ends of the piston; first coating material applying means installed above the rotation support means in a manner such that it can be moved upward and downward, the first coating material applying means having a first nozzle which applies coating material to a circumferential outer surface of a head part of the piston rotated by the rotation support means, and at the same time spreads to a uniform film thickness applied coating material and thereby removes excess coating material, in a state where the first nozzle is placed adjacent to the circumferential outer surface of the head part of the piston; fixing means installed in the vicinity of the rotation support means to fixedly support both ends of the piston; and second coating material applying means installed above the fixing means in a manner such that it can be moved upward and downward and slid laterally, the second coating material applying means having a third nozzle which applies coating material to both wing parts of the piston fixedly supported by the fixing means, and at the same time is slid to spread to a uniform film thickness applied coating material and thereby remove excess coating material, in a state where the third nozzle is placed adjacent to the wing parts of the piston.
In the compressor piston coating apparatus according to this aspect of the present invention, in order to allow a half-finished product comprising a pair of unseparated pistons, which is prepared in the course of manufacturing a piston for a variable displacement swash plate type compressor prior to being cut into two pistons, to be properly coated, third coating material applying means capable of coating one of two head parts of the half-finished product comprising the pair of unseparated pistons can be included. In this case, it is preferred that the third coating material applying means has the same construction as the first coating material applying means.
According to still another aspect of the present invention, there is provided a method for coating the piston for the variable displacement swash plate type compressor, by the compressor piston coating apparatus to which another one of the above-mentioned nozzles is applied, the method comprising the steps of: rotatably supporting both ends of the piston by rotation support means; lowering the first coating material applying means so that coating material spreading means of the first nozzle is placed adjacent to the head part of the piston; injecting coating material to the head part of the piston through the first nozzle of the first coating material applying means while rotating the piston, and spreading to a uniform film thickness coating material applied to the head part of the piston and thereby removing excess coating material by coating material spreading means of the first nozzle; raising the first coating material applying means; conveying the piston with the coated head part from the rotation support means to the fixing means by conveying means and fixedly supporting both ends of the piston by the fixing means; lowering the second coating material applying means so that respective coating material spreading means of the second nozzle are placed adjacent to both wing parts of the piston supported by the fixing means; and injecting coating material to the wing parts of the piston through the second nozzle while sliding the second coating material applying means in an axial direction of the piston, and spreading to a uniform film thickness coating material applied to the wing parts of the piston and thereby removing excess coating material by respective coating material spreading means of the second nozzle.
According to yet still another aspect of the present invention, there is provided a method for coating the half-finished product which is prepared in the course of manufacturing a piston for a variable displacement swash plate type compressor, by the compressor piston coating apparatus to which another one of the above-mentioned nozzles is applied, the method comprising the steps of: rotatably supporting both ends of the half-finished product comprising the pair of unseparated pistons by the rotation support means; lowering the first and third coating material applying means so that coating material spreading means of their respective first nozzles are placed adjacent to the head parts of the half-finished product comprising the pair of unseparated pistons; injecting coating material to the head parts of the half-finished product through the first nozzles of the first and third coating material applying means while rotating the half-finished product, and spreading to a uniform film thickness coating material applied to the head parts of the half-finished product comprising the pair of unseparated pistons and thereby removing excess coating material by respective coating material spreading means of the first nozzles; raising the first and third coating material applying means; conveying the half-finished product with the coated head parts from the rotation support means to the fixing means by conveying means and fixedly supporting both ends of the half-finished product by the fixing means; lowering the second coating material applying means so that respective coating material spreading means of the third nozzle are placed adjacent to the two pairs of wing parts of the half-finished product supported by the fixing means in a state where the two pairs of wing parts are positioned at a center portion of the half-finished product and are not separated from each other; and injecting coating material to the wing parts of the half-finished product through the third nozzle while sliding the second coating material applying means in an axial direction of the half-finished product, and spreading to a uniform film thickness coating material applied to the wing parts of the half-finished product and thereby removing excess coating material by respective coating material spreading means of the third nozzle.